  #include "CImg.h"
  using namespace cimg_library;

  int main() {
    CImg<unsigned char> image("lena.png"), visu(500,400,1,3,0);
    const unsigned char red[] = { 255,0,0 }, green[] = { 0,255,0 }, blue[] = { 0,0,255 };
    image.blur(2.5);
    CImgDisplay main_disp(image,"Click a point"), draw_disp(visu,"Intensity profile");
    while (!main_disp.is_closed() && !draw_disp.is_closed()) {
      main_disp.wait();
      if (main_disp.button() && main_disp.mouse_y()>=0) {
        const int y = main_disp.mouse_y();
        visu.fill(0).draw_graph(image.get_crop(0,y,0,0,image.width()-1,y,0,0),red,1,1,0,255,0);
        visu.draw_graph(image.get_crop(0,y,0,1,image.width()-1,y,0,1),green,1,1,0,255,0);
        visu.draw_graph(image.get_crop(0,y,0,2,image.width()-1,y,0,2),blue,1,1,0,255,0).display(draw_disp);
        }
      }
    return 0;
  }
